Certain microelectronic packages are made using a sheet-like element incorporating a dielectric layer and mounting terminals disposed on the element. Some or all of the terminals are connected to a microelectronic device which is assembled with the sheet-like element in a package. Various proposals have been advanced for stacking plural chips one above the other in a common package. One such arrangement includes a substrate having a dielectric structure substantially larger in area than the area of a single microelectronic device or chip. Several microelectronic devices are mounted to the substrate in different areas of the substrate and the substrate is folded so that the various microelectronic devices are stacked one above the other and so that the mounting terminals on the substrate are disposed at the bottom of the stack. Typically, the substrate has electrically conductive traces extending along the dielectric structure. These traces connect the microelectronic devices with one another, with the mounting terminals, or both, in the completed structure.
The substrate must be folded in precisely the right configuration so that the various microelectronic devices will be disposed in the correct locations, one above the other. The entire package could be placed in an area of a circuit board only slightly larger than the area occupied by a single microelectronic device. However, inaccuracies in folding the substrate can cause parts of the package to lie in positions different from their intended position relative to the mounting terminals. This effectively increases the overall size of the package. Neighboring components mounted to the circuit board must be located at a larger distance from the stack so as to provide clearance sufficient to accommodate this internal misalignment within the stack. Moreover, the piece-to-piece differences between individual packages caused by folding inaccuracies can complicate the task of handling and feeding the stacked packages during automated assembly operation as, for example, during mounting to the circuit panel.
It is desirable to provide further improvements in stacked microelectronic assemblies and methods of forming the same.